Fluid propelled airplane



Dec. 14, 1954 A. M. LIPPISCH 2,696,953

FLUID PROPELLED AIRPLANE Filed March 9, 1951 2 Sheeiis-Sheet l INVENTQR.

BYALEXANDER M l/PPIscH AT TORNE v Dec. 14, 1954 sc 2,696,953

FLUID PROPELLED AIRPLANE Filed March 9, 1951 2 Sheets-Sheet 2 INVENTOR. V BYALEXAMQER Mllpp'lscn T TORNE v United States Patent F PROREILIMEDLAHPMSNELE Alexander ML, Lippisc hi, Cedar: Rapids; Iowa, assi n Collins Radio Company,.Cedan Rapids lhwa gar.corporation oflowal must be such that: it doesnot-hib the ground whensthe Y plane istina landing attitude-.- The problemistherefore presented of gettingthe maximum amountof power -ihto" a propeller of fixed; diameter.-

lt is an. object-of this invention, therefore, to provide means for increasing-the thrustobtainablee'witli zit-propeller ofrfixedj diameter.

Anotherobject of thiQ'iI IVeDtlOHET SiIG" eliminate-torque? resulting fromrotation of apropellen and its" p ower' plantt- Still; another object of this: invention; istoy-greatlYiir crease the efiiciency of apropell'ert Yet another objectof= this invention is toprovidei at shrouded propeller wherein theconfigurationofitheshroud incombination withthe-'propeller-gives: agreatly'increased thrust as: compared to-an open propeller-;-

A featureof this inventiomis-found in the-provision: fort a propeller mounted in a" tube-which has the shape: of an air-foil-section so as: to; obtaina greatly increasedl efli'ciency for the propeller;

Further, objects, features and acl'vantagessofthisfiiiven tion will become apparent fr'om the:followingdescription and claims when read in -view of"the drawings, inwhiclrz Figure 1 illustratesa cross-sectional view.,oftarr,air-fbil section tube-with aapropeller mountedtlierein;

Figure ZiIIustrates-asectional view'tl'irough an air=foil'-- section -tube with'adriving means,- propellenand straight-"- eningthaifiesrnounted therein;-

Figure 3-is a-sectionalfview-of an air-*foilisectiontube with two propellersand counter baflies mountedtherein;

Figure 4 is, asectional view. takenoma line-k430i" Figure 5 l and illustrates the power pltmtaof thisinvention: mounted in a delta wing aircraft;

Figure 5 isa: rear; view of a-delta wing aircraftfand Figure 61 is a sectional-view= taken on: line 6"6'.'-' of? Figure 4.-

The ideal f efiiciency of P anopen propeller (one= which; is *unsurrounded by any-material) isgivenaby theequationewhere CT is defined as; the disc,loa ding.,coefiicientcandli is determined by:

Wide :11

The reduction of. the propeller: diameter has its largest influence in the low speed range where the stagnation pressure/is low-:andythe. low speed thrust; is considerably reduced because there is too high disc loading. The,reduction of the staticzandlow speedwthnustihas a verv bad influence on the length ofthe take-ofi run especially with high speed airplane configurations Which'necessarily have: hightwing loadings.

Applicanttha-s. discoveredwthat the. effi'ciency of a pro:-- peller can be substantially increased by mounting it in a tube with a cross-sectional-configmation such as shown in Figure 1. Figurefll illustratesuattube' 10 which is formed with a forwardly curved portion 11 that joins a straight section. Tube 10 might be described as trumpet-shaped and in thickness represents an ainrfoil-section as shown.

A propeller 13 ismounted in the tube adjacent the inner end of the straightsection 1-2; The propeller'is" driven by a suitable-adriying means, not shown in Figure 1 for the reason that this figure is'used to illustrate the theoretical principles of the invention.

Air is impelled through. the tube 10 in the direction of the arrows. Assuming. thaLthe outside air forwardlyv of the tube 10 has a pressure of Po and a velocity of V0, thenthepropellenll'r. will draw. air. into, the tube-10 and increase, its velocity to.- Vnand decrease, its. pressure. to P. The propeller increases the pressure without changing the. velocity -which.must stay constant in a tube. of constant cross-section. The pressure behind the propeller must be.

equal to the outside pressure and from the theory'of How it is known that this static pressure must be the sameas. the external pressure P0. The pressure differential created by the prop therefore is:"

( AP=P -P According to Bernoullis lam' theiin'coming flovwis described by:

Thrust developed by the propeller 13 and tube 10 is equal to -tlierincreasedn mommrtum-om 7 TaMJVi-Vd) I where T is thrust and-Mss-isthemass per second which is accelerated and is equal to:

Substituting; the: value; of: obtained; from v Equation:

The power required to compress the air going through the propeller from P up to P is equal to the volume per second times the pressure differential required or:

Substituting the value of Po-P from Equation 6,

15 1r Power=g V (VV3);D

is obtained.

The efiiciency is defined as the ratio of output or effective power to the necessary required input power:

T hrust X speed 0 from Equation 13 and multiplying numerator and denominator by two gives:

Comparing the open propeller with a propeller in a tube having the same thrust coefficient we obtain the equation:

tube V 'i T From this formula it is observed that approaching zero speed where CT approaches infinity, the efficiency ratio becomes the square root of 2 which equals 1.414. Thus the theoretical increase in efficiency of the propeller in a tube is 41% greater than the efficiency of an open propeller.

The ratio of thrust in the two cases is {/2 or 1.260. Thus, a theoretical increase of 26% in the static thrust is obtained over an open tube. The increase in thrust is due in part to configuration of the tube. Lift is developed normal to an air-foil-section and on the curved portion 11, the lift vector L, extends slightly in the forward direction. This gives a forward lift component Lx and a lateral lift component Ly. The lateral lift components Ly are balanced by components about the periphery, but the forward components Lx add together to give a forward thrust.

Applicants Figure 2 illustrates a practical embodiment for the principles illustrated in Figure 1. The tube 10 is generally trumpet-shaped, as in Figure 1, and has mounted within the larger portion 11, a driving means 14 which is supported within the tube by holding brackets 16. The forward end of the driving means 14 has a streamlined projection 17 so as to maintain smooth flow 1 by the driving means. The output shaft 18 of the driving means 14 is connected to a propeller 13 which is mounted at the end of the curved portion 11. It is to be understood that the curved portion 11 must be convex to obtain the advantages of the invention.

Mounted rearwardly of the propeller 13 in the straight 86 uDen 4 portion of the tubes 12 are a plurality of counter vanes 19. These counter vanes are set so as to deflect the flow of air through the tube and to eliminate the rotational motion caused by the propeller 13. The vanes 19 are formed so as to be air foil sections, as shown by the section 21 through the vane. The vanes in addition to straightening out the flow of fluid through the tube, also exert a forward thrust on the tube 10 due to their air foil configuration. There will be a forward thrust component developed on the vanes in a manner similar to the forward thrust LX developed on the curved portion 11.

A longitudinal rod 22 is fastened to the junction point of the vanes 19 and has an outwardly extending end 23 which comes to a point to obtain a streamlined air flow. The opposite end of the member 22 is rotatably connected to the shaft 18 to give it longitudinal support.

Applicant has discovered that the increase in static thrust of his apparatus shown in Figure 2 over an open propeller of the same size is greater than the theoretical increase of 26% and was in fact more than 30%. One reason for this increase is that in the open prop there is usually no recovery of the rotational momentum of the slip stream. Applicants vanes 19 obtain lift from the rotational components of slip stream and thus increase the efficiency. The propeller in the tube also has a lower disc loading for the same thrust conditions. The thrust developed by the propeller in the tube is due to the pressure differential on opposite sides of the propeller and also from the suction obtained due to the trumpet-shaped intake 11 and the configuration of the vanes 21.

The power plant illustrated in Figure 2 is designed for speeds up to the transonic zone. For example, the power plant could be mounted in the wings of an aircraft, or it might be mounted rearwardly on top of the fuselage and extend upward above the fuselage.

For high speed flight propulsion, however, the upwardly extending power plant and tube would be unfavorable because the configuration of the front of the tube would develop a shock wave and greatly increase drag. Under such conditions it is deemed advisable to mount the power plant within the fuselage of the aircraft, as shown in Figure 3.

Figure 3 illustrates the fuselage of an aircraft designated generally as 26 which has mounted therein by the brackets 27 a driving means 28. A tube 36 similar to tube 10 of Figure 2 is connected to the fuselage 26 with longitudinal supporting means 35. The driving means 28 has an output shaft 29 which extends rearwardly into tube 36 and has mounted thereon a pair of propellers 31 and 32. Air-foil-section counter vanes 33 and 34 are mounted to the tube 36 behind the propellers 31 and 32, respectively.

The shaft 29 passes through bearing means 37 at the junction of the vanes 33, and is rotatably supported by bearings 38 at the junction of vanes 34. A rearwardly extending streamlining portion 39 extends from the junction of the vanes 34 back through the tube 36.

The tube 36 is formed with a forwardly convex portion 41 and a rear straight portion 42. The propellers 31 and 32 and vanes 33 and 34 are mounted within the straight portion 42.

Mounted forwardly of the curved portion 41 of tube 36 are a plurality of baffies 44 which are supported by the longitudinal supporting means 35 and are off-set longitudinally of each other so as to direct air through the throat 41 of the tube 36. The bafiies 44 are formed into air-foil-sections such that the air rushing past them and into the throat 41 of the tube will give a forward lift component. A forward component of lift is also developed on the counter vanes 33 and 34. The dual propellers allow greater thrust to be obtained from the apparatus.

Figure 4 illustrates a power plant of this invention installed in a transonic aircraft of the delta wing type.

The delta wing aircraft has a torpedo shaped fuselage 46 which has a triangular wing 47 mounted rearwardly. The rear end of the fuselage is formed into a tube 36 such as shown in Figure 3. The baffles 44 shown in Figure 3 are retained in this configuration but they have been formed to extend outwardly into the wings on the upper and lower surfaces so that more air can be sucked down into the tube 36. Only one propeler 31 and one set of counter vanes 33 are illustrated in Figure 4, but it is to be understood that any number of propellers and counter vanes may be installed. The bafiies 44 extend into the wing sections and thus draw some of the air from the boundary layer through the tube 36. This increases the stall resistance anddecreases the drag on the wing 47. To more clearly understand the shape of the bafiles illustrated in Figure 4, reference may be had to Figure 6 which is a sectional view taken on a line 6-6 of Figure 4 and illustrates the upper and lower baflles 44 mounted in the fuselage 46 and the wing 47. The bafiles 44 comprise round portions 45 and straight portions 50. Longitudinal support means 35 are used to support the tube 36 and bafiles 44. It is important to note that the curvature of the baffles 44 must be ofthe same general shape as the curved portion 41 of the tube 36. Only this configuration gives a forward lift component Lx from the baflles 44. This lift component developed on the bafiles 44, the throat 41, and the counter vanes 33 aids to increase the efliciency of the unit.

An advantage obtained by applicants power plant not heretofore mentioned is that substantially all torque from the rotating engine 14 and propeller 13 is eliminated by counter vanes 33. With reference to Figure 2 it is seen that torque developed by the propeller 13 and engine 14 is transferred to the tube 10 through the support means 16. However, counter vanes 19 intercept the rotating energy of the propeller 13 and exert a torque on the tube 10 which is opposite to the torque developed by the engine 14 and the propeller 13. In that the torque produced on the vanes 19 is substantially equal to the torque produced by the engine 14 and the propeller 13, the torque will be eliminated in the tube 10 between the mounting 16 and the vanes 19, and thus the pilot does not feel any torque. This is a great advantage, especially in aircraft of high wing loading and high power wherein the torque has been known to actually spin the plane about a longitudinal axis. The torque in applicants invention will be dissipated in torsional stress in the tube. In the embodiment of Figures 3 and 4 the torque is dissipated between the motor supports and the counter vanes.

Although this invention has been described with respect to preferred embodiments thereof it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

1. An aircraft comprising a fuselage and wings, a trumpet-shaped tube constituting a rear portion of said fuselage, a plurality of baffles forwardly of said tube for supplying air to said tube, said baffles formed so as to be air-foil-shaped in cross-section and with the forward side of said bafiles having a greater camber than the rear side, said baffles comprising upper and lower baffles which have semi-circular mid-portions formed in said fuselage and straight end portions adjoining either side of the mid-portions, said bafiles defining passages communicating with the exterior of said fuselage and the interior of said tube, a driving means mounted to said fuselage, and a propeller mounted on an output shaft of said driving means within the tube.

2. An aircraft comprising a fuselage and wings, a trumpet-shaped tube constituting a rear portion of said fuselage and supported by longitudinal supports extending to a center portion of said fuselage, the wings of said aircraft connected oppositely to the rear and center portions of said fuselage, a plurality of baffles mounted to said longitudinal supports and extending into the wing on the upper and lower sides, said bafiles defining passages communicating with the exterior of said fuselage and the interior of said tube, said baffles air-foil-shaped in section and with the forward side having a greater camber than the rear side so as to draw air into said tube and create a forward lift component, a driving means mounted in said center portion of said fuselage and having an output shaft which extends rearwardly within said tube, a propeller mounted on said shaft within said tube, and a counter vane assembly mounted to said tube behind said propeller to remove the rotational energy imparted to air by said propeller.

3. An aircraft comprising a fuselage and wings, a trumpet-shaped tube constituting the rear portion of said fuselage and supported by longitudinal supports extending to a center portion of the fuselage, the wings of said aircraft connected oppositely to the rear and center portions of said fuselage, a plurality of baffies mounted to said longitudinal supports and extending into the wing on the upper and lower sides thereof, said baffles airfoil-shaped in section and having a center curved portion conforming to the shape of the fuselage and straight end sections received into opposite wings of the aircraft and joining the curved sections, the forward sides of said bafiles having a greater camber than the rear sides to draw air into said tube and creating a forward lift component, said bafiles defining passages communicating with the exterior of said fuselage and the interior of said tube, a driving means mounted in said fuselage and having an output shaft which extends within said tube, a propeller mounted on said shaft within said tube, and a countervane assembly mounted to said tube behind said propeller to remove the rotational energy imparted to the air by said propeller.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,375,601 Morize Apr. 19, 1921 2,477,637 Mercier Aug. 2, 1949 FOREIGN PATENTS Number Country Date 515,469 Great Britain Dec. 6, 1939 

